Semiautomatic telephone system



April 1, 24,341 E. E. HINRICHSEN SEMIAUTOMATIC TELEPHONE SYSTEM Filed Feb. 27. 1925 14 Sheets-Sheet 2 1,624,341 AP"! 12 1927' E. E. HINRICHSEN SEMIAUTOMATIC TELEPHONE SYSTEM Filed Feb. 27. 1925 l4 Shee ts-Sheet 3 April 12, 1927,

' E. E. HINRICHSEN SEMIAUTOMATIC TELEPHONE SYSTEM Filed 27. 1925 14 Sheets-Sheet 4 1,624,341 12 E. E. HINRICHSEN SEMIAUTOMATIC TELEPHONE SYSTEM Filed Feb. 27, 1925 14 Sheets-Sheet 5 SEMIAUTOMATI C TELEPHONE SYSTEM Filed Feb. 27. 1925 14 Sheets-Sheet 6 UNITS TENS V [award [2' Mkmb/rsen by Afiy April 12, 1927.

1,624,341 E. E. HINRICHSEN SEMIAUTOMATIC TELEPHONE SYSTEM Filed Feb. 27. 1925 14 Sheets-Sheet 7 April 12,1927. 1,624,341

E. E. HINRICHSEN SEMIAUTOMAT IC TELEPHONE SYSTEM Filed Feb. 27. 1925 14 Sheets-Sheet 8 April 12, 1927.

E. E. HINRICHSEN SEMIAUTOMATIC TELEPHONE SYSTEM Filed Feb. 27, 1925 14 Sheets-Sheet 9 1,624,341 1927' E. E. HINRICHSEN SEMIAUTOMATIC TELEPHONE SYSTEM Filed Feb. 27.. 1925 14 Sheets-Sheet l0 A til 1 1927.

p 2 E. E. HINRICHSEN SEMIAUTQMAZTIC TELEEPHONE SYSTEM Filed Feb. 27. 1925 14 Sheets-Sheet '11 April 12 1927. I 1,624,341

5. E. HINRICHSEN SEMIAUTOMATI G TELEPHONE SYSTEM Filed -Feb. 27. 1925 14 Sheets-Sheet 12 by W'A/fy April 12 1927. 1,624,341

E. E. HINRICHSEN SEMIAUTOMATIC TELEPHONE SYSTEM Filed Feb. 27; 1925 14 Sheets-Sheet 13 INCOMING BRUSH FINAL BRUSH Wye/#011: fdn ard if fi/mclzsen April 12 1927.

r E. E. HINRICHSEN SEMIAUTOMATIC TELEPHONE SYSTEM Filed Feb. 27. 1925 14 Sheets-Sheet 14 Inge/77*: fdward {j' zy/lr/msm Patented Apr. 12, 1927.

"UNITED STATES EDVJARD E. HINRICPZSEN; NEW YORK, N.

" PATENT OFFICE.

Y., ASSIGNOR, BY MESNE ASSIGNMENTS,

TO WESTERN ELECTRIC COMPAISIY, INOORIOR-ATED, A CORPORATION OF NEW YORK.

SEMIAUTOMATIC TELEPHONE. SYSTEM.

Application filed February 27, 1925.

This invention relates to telephone exi-hange systems and particularly to systems in which connections are established in part by operators and in part by machine switching apparatus.

' The object of the invention is to improve 1 the organization of selecting and controlling mechanism in-a system of the foregoing character where trunks leading from an operators position to automatic switches are identified to the operator for use.

A feature of the invention relates to a system in which an'operator by'setting up a designation on her keyboard causes an: idle sender and an idle marker to become associated with such position, each receiving therefrom a separate portion of said designation, the marker serving to select an idle outgoing trunk and to cause an indication thereof to the operator and thesender serving tocontrol' switches or other responsive mechanism at the distant end of such trunk.

Another teature'relates to a sender for use in a' system of this character which is aoapted to control switches of the power driven type by revertive impulses or to send direct code impulses to control switches of the coordinate type'in the distant'ottice.

A further .teature'resides in the means for so translating the numbering or the trunks they appear on the-selector frame vertical into the numbering of the corresponding trunks as they appearin the multiple at the operators position. as "Other and further features contemplated by the presentinvention will be more clearly understood from thet'ollowing detailed desrription and from the appended claims.

Referring, to the drawing, Figs. 11to 13, taken in the order'shown inFig. 1e, illustrate a system embodying theprinciples of this invention. i

Fig. 1 shows thekey equipment at the operators position. F ig. 2 illustrates a position finder switch ot' the coordinate type which-serves to connect an idle sender with the key set of an operators position. v V

Fig. 3 shows the" position connector cir- (Hit which is'employed herein to connect an idle marker with the operators key set.

Fig. i discloses the magk'erz translating circuit which is providedfor'translat-ing the Serial No. 1 1,960.

ofi ice code to determine in response to the oflice code transmit-ted, the class of trunks necessary for the completion of the call and for connecting a desired trunk group in such class extending to the desired ohice.

Fig. 5 represents the marker selection circuit in which the marker selects an idle trunk and holds it in readiness for connection.

This figure also. represents the means for translating the number of the seized trunk on the selector frame vertical into the numbering of the corresponding trunk jack that appears in the trunk multiple at the operators position.

F ig. 6 illustrates the trunk indicator at the operators position, which displays the number of the seized trunk as it appears in the multiple.

Fig. 7 discloses the trunk and frame connectorswhich serve to connect. the marker with the selector switch frame in which appears the desired group and to switch such group for testing.

Fig. 8 shows a sender connector circuit and the ofiice code registers of the sender. This figure also shows the trunk group equipment which is provided for the purpose of holding the desired group of trunks busy until the marker has completed its operations and is released.

Fig. 9 illustrates the sender numerical registers which are connected through the position finder switch shown in Fig. 2 with the numerical keys in the operators position.

Fig. 10 shows the Selector switch of the coordinate type, at which the outgoing trunks terminate. This figure also shows a relative arrangement of the calling subscribers station, the operators cord and the outgoing trunk jacks, also the incoming and the final frames of the coordinate type, and the incoming and the final selectors of the panel type in the terminating oilices and a called suhscribers station of each.

Fig. 11 discloses the impulsing circuits in which the class of call circuityestablished by the translator relays shown in F ig. 4, connects the necessary apparatus and controls the transmission of the necessary impulses for the proper completion of the call.

Fig. 12 shows the panel revertive pulsecounting circuit for calls direct to a panel type office.

Fig. 13 illustrates the panel register circuit.

Fig. .11 represents a diagraininatical arrangement of the various figures of the drawln rs in their relative positions.

Fig. a diagram showing the general arrangement of the various major pieces of apparatus required and shows the relation which the various pieces of apparatus bear to one another. l he specific control circu'ts en oinitted. but it is believed that an inding of the general plan of operation of the system may be understood from the following descriptioi'i.

llelerrinp" first to 15, a subscribers line connected with a station 1501 enters the exchange and has its appearance. in an answering jack 1553.1 at an operatous position 1503. The operator by means of one of her position cords as 1:702 connects her head set (not shown) with the suhscribefs station, inquires tor the number 011 the called subscriber-s line and sets up the call accordingly on her position hey set. The operation of the keys for the ollice designation ell'ects the operation of a position connector 1530i which individual to position 1503, to seize an idle llltll'licl' ot the group represented by 15013 and 1507. A position tinder switch 15Gb which common to a plurality of positions is also operated to connect an idle sender oi? a group represented by 1509 and 1510. lhe seizure oi. the marker ell'ects the operation of a selnler-connector 1511 which inter-connects the seized marks and seized sender. The marker is arranged to receive the oliice code designation and to make the necessary translation thereof for the purpose oil determining the class of trunlrs required for the completion of the call. and selectinp a group of trunks in said class which extend to the desired oliice, and is further arranged to operate a trunk connector 1512 and a frame connector 1513 so as to connectv itseljli with the selected group 01' trunlts and to a trunk selector t'rame 1511 at which the selected group terminates. 'lhe testing equipment; in the marker tests the said group of tlllllliS for busy conditions 1 when an idle trunk is found its assoand "iated operating mechanism at the selector frame is actuated to connect the seized sender with the idle trunk. The marker is also arranged to translate the position number of the i ed idle trunk at the selector Frame into its corresponding position inunher as it appears at the operatofs position and to display, the latter number at the l 'lhe sender arranged to trrn-c indicator. receive the numerical designation over the operated contacts ol the position tinder switch and to transmit the necessary i111- pulscs over the seized trunk. In response to these impulses, the apparatus in a distantoll'ice, such as 1519 or 1520, which are re spectively representative of the panel or the coordinate machine switching type, is actuated to connect the ailed subscribefis line to the seized trunk. Trunks 1515 and 1516 represent agroup oli trnnlzs extending to otlice .1519, and trunks 1517 and 1518 represent a group which extends to an ollice 1520. Other p rou 'is may extend to other types 01' olllces. Each of the outgoing trunks also terminates in a jack such as 1521, 1522, etc, at the operators position and when the number of the seized trunk is displayed at the indicator, the operator by means of the free end of cord 1502 connects the calling: suhscriber"s line with the seized trunk. When the operator connects the cord 15052 to the jack which is associated with the seized trunk, and the apparatus at the distant oi" lice has completed its operation, a connection is established between the calling and called suhscribefls lines.

In the case 01 an ollice equipped. with switches of the coordiinlte type the senders 1509, 1510 are arranged to send'code i111 pulses to a sender such as 1530 at the distant oti'ice, which through the agency of a nrarln or as .1531 controls the switches. For further details in this method of operation relierence is made to the application 01" S. ll. lVillianis and E. S. Gibson, Serial No. (5 1-5,- 011, tiled June 11:3, 1923, Patent No. 1,515,967, issued June 30, 1925. Also the senders 150$), 1510 etc, are designed to control call indicators at distant ollices as shown in the patent to S. B. lVillianis No. 1,517,331 granted llleceniber 2, 1924:.

General description of the sysfimn mid apparatus.

Referring first; to Fig. 10, the receiver at the subscribers station is removed from the hook and the lamp associated with the subscriber-s answering jack at the operators position lights, indicating to the operator that a connection is desired. The operator inserts the calling end of one 01? the position cords into the answering jack and receires the number of the called party. Referring now to Fig. 1, the operator depresses the otlice code keys corresponding to the code of the ofiice in which the called partys line terurinates, or an individual ollice key it one is provided for the desired ollice, and a start circuit is closed, thereby effecting the seizure of an idle sender and an idle marker. The seized sender is connected to the numerical keys of the calling position by a position tinder switch of the coordinate type, and is also connected to the seized marker by means of a relay or a group of relays. At the $211116 time the position is connected direct to the marker by means 01 a, inulti-contaet relay. Simultaneously the position is connected direct; to the marker by means of another multi-contact relay which also establishes circuits for transferring the oflice code registration to the marker and for operating the position trunk indicator in accordance with the trunk selected. The marker makes the necessary t-ranslationof the ofiice code and tests the corresponding group of outgoing trunks, and connects the first idle one at the selection of any trunk depends, of

course, on the position of that trunk on the selector vertical, and this position does not bear any fixed relation to the number ofthe multiple ack to which the trunk is con nected. In fact, if the trunks are multiplied, as would be the case of small groups, the circuitsmust be so arranged that the same indication will be given for any particular trunk, no matter in which of its positions at the coordinate frame connection is made. This is taken care of by connecting the contacts of the testrelays to the translating relays through contacts of the relays which connect the testing apparatus to the trunk group. Cross-connection facilities are I provided so that the selection of any trunk in any group will cause the display of the proper number without requiring a definite or fixed relation between the position of the trunk at the selector frame and its number in the operators multiple. The marker is also arranged, to transmit a class indication to the sender and to register the ofiice code in the sender in case the system is used in connection with tandem trunks.

As soon as the marker has found an idle trunk in the desired group and connected it to the sender, and has causedthe display of the trunk number on the position trunk indicator, it is released so as to be ready for other connections. The number of the desired. line is set up on a single set of numerical keys by the operator and registered on relays in the sender. Four wires, however, are used for operating the register relays, and the circuits are so arranged that no marginal features are involved. As soon as the numberhas been set up, the sender proceeds to send out impulses over the trunk to operate the distant switches.

The sender in the system shown is ar ranged to control calls of the following classes:

1. Direct to the panel type central ofiices.

2. Direct to call indicator equipments in manually operated offices and in both coordinate and panel machine switching offices, having incoming senders.

- 3. Direct to a tandem office where the complete subscribers number is recorded in a tandem sender.

4. Direct to a tandem oflice where the office code only is recorded in the tandem sender and the numerical code is recorded in and sent by the sender in the originating oflice to control the switching at the terminating office.

As soon as the operator plugs into the trunk jack whose number is displayed, the indicator lamps are extinguished, the connection between a position equipment and the sender is broken down, and the posit-ion equipment is restored to normal. The sender remains connected-to av trunk until it has finishedsetting up the connection. It then causes the trunk conductors to be closed through to the multiple jackand releases. In case the sender finishes its work before the operator plugs in, it holds the trunk until it is taken up in the multiple, and then immediately completes it, and releases.

The coordinate switches shown in this system may be of the cinstruction such as described in the patent to S. B. Williams, No. 1,517,331 issued December 2, 1924.

Detail description of the operation.

It is assumed that the subscriber at station 1021, whose line terminates in an ofiice equipped with a key indicator system, desires to hold a conversation with a subscriber in a distant office, whose line number, including the ofiice code designation, is 99'7 1236. It is also assumed that the called subscribers line may terminate in any of the offices to which calls of the above enumerated classes can be completed. Although no mention is made of a call being completed through a step-by-step ofiice, this system can be readily adapted to establish the connection for such a call with very few minor changes in the circuits.

when the operator has received the number of the called subscriber, the call is set up on keys which are common to the operators position by depressing, first, the keys corresponding to the code of the particular oiiice in which the desired line terminates, which in this case, for illustration, will be i), 9 and 7 shown in Fig. 1 in the rows A, B and C respectively, and second the numerical keys 1, 2, 3 and 6 corresponding to the numerical designation of the called subscribers line shown in row D. However, the depressing of the numerical keys is not done until the operator has received the usual signals informing her that an idle sender is seized. The operation of keys 9, 9 and 7 close obvious operating circuits for their respectively and individually associated relays 119, 129 and 137. These relays operated and locked in parallel circuits extendingthrough the windings of relays 141, 142 and Iii fail

1.423 renpectively, common conductor 156, i nncr right normal (Oil'ttCt of relay 14-9, to groin'ul at the right armature ot relay lit, but because of the shunt existing; in the original operating circuit for relays 1,19, jlilll and 137 the lockingcircuits are inell'ec' tire to cause the operation of relays l-ill, and lll'l. hen the keys are released and the shunt circuit is opened relays lit-l, Lil.- and H3 which are common to their 1'e- :zpcclire rows of keys A, B and (I, ope'ute. t lhould, at this time when relays lell, 14-2 and ill? are operated. the operator in or or depress a second he in any row a. circuit would he closed through the vindiup of relay t lt and this rel: would opufate. The operation of relay till would cause the operation oi wipe-out relay l l-l, and relays lit), 12% and 13'? together with relays l-ll, i l-:2 and lie would subseipu-intly release therein wiping: out all the connections already estab' lished and the operator would now proceed with a new set-up. A key lfii is also proridcd a: rach operators position for the pu 'i iose oi. wiping out the coronation iii she should desire to do no, the relar' l-llbeing: operated in this case also to etlcrt the dirconnection.

In large .uuiltioilice areas the operators positions are also equipped with individual other keys such as 101 and 102, one lief," being; provided for each of those oliices to which the tr; tile is heavy.

When the relays 14:1, 142 and M3 operate they close at their upper contacts an obvious operating: circuit for the start. relay l i-5.

l-telay lit) operates and closes at its inner contact an operating circuit for the notrunh hunp (30h the circuit being tracuible from battery, through the lamp (301., right and left burl: contacts oi relay (5052, condin-tor 003, to ground at the inner armature o'l? relay 14,51. Lamp G01. r-xhich is individual lo the ope ator s position, lights indicating that the start circuit; is functioning to connect an idle trunk with the operator's POf-lllion. .lt the middle contact ol' relay l-lzi a circuit is closed to operate the sender lamp lfil'T, the circuit. brine; traceable from ground at the middle armature cl? relay ill), outer leftbill'li contact oi relay l-lS, inner left back cont: ct of relay H9, right back contact ol. relay 148, through the lamp 1e 7, to battery. The lamp 14-? lights indicating that the start circuit is seeking; an idle slender. A lso at the middle contact of relay ill?) an operatii'ig circuit for the rn'tical group relay Bill of the position tinder switch 200 is closed and is parallel to the circuit, just traced, up to the inner left back contact of relay ill) at which point the circuit lior relay Elli extends over the outer left back contact of relay ill), conductor 150, upper winding of relay 1201. to battery at the outer llt'lllarl iaturc of relay QUE). Re-

lay 201 operates and locks in a circuit extending; through its lower winding; and front contact, lower back contact of relayQQiZ, conductor 25.30, tl rough the winding of relay 20?} to battery, and relay 9025 ope 'atcs. :ltela LUl common to all the operators positions on one vertical. and in this case, it llE-isllllltll to serrc position Rte. 1 together with its associated rertical magnet 20 described below, to prepare the connection of position No. l with the position tinder switch through the operation oil. the list vertical group of contact sets 221 to 227 iuclucire. ltelay 201: iu likewh-e con'unon to a group ol' operi iors' positions and operates .nnilarly to cause the second rcrti all group or" contact sets to prepare a connection between :1 uneition in itu respective n rou l and the porn ion lind r :er-xitch. Relay 2015 is common to all the vertical group relays on the switch, which are associated with the ope atone position, and provides the means for closing: the ope ating' circuits for the rerticul illllgg'llol'h' which operate the groups ot con act sets. clhould relays Bill and 2052 operate si:nultaneously, relaf .2013 would be the only relay ol' the two able to lock inure much as the origii'n'al operating" circuit for relay 202 would cause a break in the locking; circuit for relzr' .301. The subsequent oper ation of relay Llli-i carried by the locking ci wait for relay 202 would open the original operating circuit for relay Qtll 5a using, it to releune and await the deenergization of relay 202 whose period of energization, as will be seen, is very short.

Assuming position 1 to he the only position traneinittii'ig a call, the operation of relay 2G3 closes at the inner le'l t armature an operating; circuit for relay 250i which operates, thereby :onnecting the associated llltll'liGl' No. 1 to the position, the circuit beint, traceable iron ground, at the outer le'tt armature of relay eon, contact ol? relay i209, conductor 2H, upper back contact ol: relay 215 of the ad *ance nun-her circuit, conductor 2LT, through the winding ol' relay Pllll, to battery. lela l'ltll opcruies and at the next to its uppermost contact ground is connected to conductor 320 to close an operating circuit for relay 50 i. ltelay 50:) operates and locks in a circuit extending over its inner right front contact, outer lelt hack contact of relay 502, left back contact of relay 506 to ground. The opera tion oi rela 5t)? closes an operating circuit tor :ul'rancc niarxer relay .215, the circuit hello); traceable from battery, through the upper winding of rela v 2 15, conductors Qlll and 50.3, to ground at the inner lelit armature of relay 503. Relay 215 ope allies and opens the original operating circuit for relay l-ltll, but relay 330i remains operated in its locking circuit extending through the wiiuling olf' relay 5209, which up to this time was shunted ill) and is now permitted to operate. Relay 203 operates and prevents relay 322 from operat-' ing, which, if permitted to operate at this time wouldengage a second marker.

hen relay 503 operates it closes an operating circuit for timing relay 5-1-1 which in conjunction with interrupter 542, lamp 543 and relay 506 comprise a timing device employed for the purpose of setting a time limit for automatically holding the equipment engaged, if for-some reason the call should be delayed or abandoned. \Vhen the time limit expires relay 506 operates andeii'ects-the operation of release relay 502 which releases the equipment.

Should marker No. 1 be busy relay 215 would be in an operated condition and the operating circuitwould now be traced from ground at the inner left armature of relay 203, over the upper front contact of-relay 21 5, upper back contact of relay'216, through the winding of relay 322, to battery and relay 322 would operate connecting marker '2 to the position. But assuming marker 1 to be lle, relay 301 operates and closes a locking circuit for itself over conductor 323, through the winding of relay 209, to ground at the outer left armature of relay 203.

Then relay 203 operated it opened the original operating circuit for relay 201 but the latter relay is maintained in an operated position over its lockingcircuitf At the inner right armature of relay 203 an operating circuit for the position vertical magnet 204 was closed, the circuit being traceable from ground at the inner rightarmature of relay 203, outerupper contact of relay 201, through-the winding of magnet 204, to battery. Atthe outer left armature of relay 203 an operating circuit for the sender vertical magnet 207 also wasclosed and this circuit is traceable from ground at the inner left armature of relay 203, contact of relay 213, conductor 210, back contact of relay 21]., through the winding of magnet 207, to battery. The closing of theoperating circuits for the magnets 204*and 207 of the position finder switch 200 causes both magnets to operate thereby preparing their respective vertical contact groups for connection, magnet 204, as abovestated, preparing to connect position 1, and magnet 207 preparing to connect its associated sender with the position. When magnet 207 operates it locks in a circuit extending over conductor 266, through the winding of re lay 213 to ground at the inner left armature of relay 203, but like relay 209 in the circuit hereinbefore traced, relay 2l3does not operate at this time on account of being shunted by the original operating circuit for magnet 207. Should magnet- 207 be in an operated condition when the call from on 1 is transmitted, relay 211 of the ce starter circuit wouldalso be in an operating circuit for sender connector relays801,802, S03 and 804, and the circuit may betraced from ground at the lower armature ofmagnet 207, conductor 233, uppermost operatedcontacts of" relay 301, conductor 302, through the windings of relays 801," 302,303 and 804 in parallel, to battery. The sender connector relays operate and lock in a circuit-extending over conductor 507 to ground at the middle leftcontact of relay 503. "The operations of relays 801, 802, 303 and 804 connect the sender which is now connected through the operated contacts of position finder switch-200 to the opera tor s position, with the seized idle marker for the purpose of receiving the designation of the desired office.

Relay 203 also closed an operating circuit for the horizontal grouprelay 151,

the circuit'being traceable from ground at the inner right armature of relay 203, inner upper contact of relay 201, conductor 152, outer contact ofrelay 145, outer right back contact of relay 149, through the winding ofirelay 151, to battery, Relay 151 Opel; ates andcloses at its inner contact an operating circuit for relay 234 which controls the' operation of the links 246, 247, etc., of"the"first group at position finder switch 200, the circuit being traceable from ground at'the inner contact of'relay 151, conductor 138, through the right hand winding of relay 234. to battery at the left arm ature ofrelay 236. Relay 234 operates and locks in a circuit extending over its lefthand winding, through the winding of relay236, to battery. Relay 236 operates and opens at its left armature the original operating circuit for relay 234. Should it be attempted from a second operators position to establish a'connection through a second group of links, such as 248, 249, etc, while relay 234 is in an operated condition, theoperating circuit for relay 235 which associated with the second operators position, is prevented from being ectablished by the operated condition of re'ay 236. will be "seen from-the drawing relay 236 is common to relays 234, 235, etc, which control the respective groups of links at position finder switch 200.

Relay236closes an operating circuit for relay 305 through the lowermost operated contacts of relay 301, conductor 303, outer contact of relay 151, conductor 23?, inner right contact of relay El i-l. right contact ot relay 236. to ground at the armature of magnet 204-. Relay 305 operates and connects marker No. 1. for a second purpose, that is, that the marker may receive the ollice code designation and select a trunk accordingly in the desired group. Relay 236 also closes at its right contact, an operating circuit for horizontal magnet 2-30, the circuit beingtracealirle from ground at the contact of magnet 20%, right contact: of relay 236, outer right contact of relay 234, conductor 218, right back contact of relay H0, through the left hand winding ot magnet 239, to battery. Magnet 239 operates and completes the connection between its associ' ated link 247 and the operated contact sets 223 and 125i which were prepared for connection by the ope 'ation of prin'iary and secondary magnets 20-} and 07. respective ly. When magnet Q39 operates and the as-:-- sociated link 2-17 is connected to the vertical contact sets and 25 a circuitextending through the relays 153 and 708 is closed, the circuit being: t'aceable from battery, through the winding of relay 153. left contact of relay 144, inner left back contact of relay 148, conductor 2M, operated contact sets 223 and 254,.conductor 710. through the left hand high resistance winding of relay 708, conductor 902, to ground at relay S-lal. Relay 708 operates hut relay 153 being marginal does not operate in this circuit inasmuch as the circuit extends through the high resistance winding of relay 708. The operation of relay 708 closes a holding circuit for magnet the circuit being traceable lrom battery. through both windings in series of magnet- 230, right hand winding of relay 2&0 conductor 200 of link 2LT, lowermostcontact of set 254-, conductor 709, to ground at the inner left contact of relay 708. Relay 24-0 operates and opens at its right hack contact the original operating circuit for magnet E230. Relay 708 also closes an ope 'atiug circuit for advance start relay 211, the circuit being traceable from hattery. through the winding; of relay 521.1, conductor T00. to ground at the inner le'l t contact of relay 708. .lelay 2-11 operates but does not lock as yet inasmuch as the locking circuit is open at the contact of relay The operation ot relay 21]. indicates that the associated sender is matured and prepares an operating circuit for magnet 208 which is associated with another sender. lilagnet .230 is now he'd operated in the circuit traced above. extending through the right hand winding: of relay 24:0 and over the test conductor 260. lVhen relay 24:0 operates it closes a locking; circuit li'or itself through its left hand winding; and left contact to ground at the right arinatiue of relay 20L bhonld it he desirous to establish a second call through the group ol. links controled by relay 234: while the first link in such group is busy, the circuit coming in over conductor 238 would lead over the right frontcontact of horizontal relay 240, through the left hand winding; of magnet 2W2, and magnet 2052 would. operate causing in turn the operation of link 24-6 and horizontal relay 203. Should all the links in this group be busy their associated relays such as 24-0. 203, etc, would he in an op erated condition and the call would be delaycd until a link is arailahle. lVhen an idle line becomes ayailaljilc its associated rcay. such as .44 l 203 etc, is deenergized by the opening of the relay holding circuit extending! over conductor E205, left contact of relay 201. through the winding of relay 204- to battery. Relay 26}: will operate and close at its inner rie'ht contact an 01 rating; circuit for relay 201. which operates and opens at its left contact: the holding circuits and at its right contact the locking circuits for the re ays 5240, 203 etc. lVhen relay 2% operates it suhstituter a ground for the locking circuits of the horizontal relays. hut through the operation of relay 261 and the suhsequeut release of relay EEG-l the substitute around is so disconnected and the relays tha are associated with idle links are. therefore, deenerg'ized and the idle links become availabc.

lvhcn relay 305 operated it connected the otllce. code relays at position 1 with the seized idle marker and closed at its operate-d contacts an operating circuit for certain relays in the marker translator circuit shown in Fig. a, the relays operated dependino; upon the ollice code relays at the operator s position tha t were energized by their respectively associated keys. in the case taken for illustration, the operated condition of relays 110, 120 and 13'? caused the operatrons ot relays elll and. 412, 4:07 and 408, and 4 2 and 1 )4, respectively.

The operation of these relays in the nnirlrcr translator circuit determines the class of trunks necessary for the proper completion ol the call and selects the desired group in that class. When relay 4L0 operates an m eratin g circuit for relay 832 of the cities register circuit shown in Fin. 8 is closed, the circuit being traceable liroin battery through the winding o'l relay 0352. contact ol' relay Sill-l. conductor slihamlt l 'l'ront contact ol relay -l-l conductor 1-. let't hack contact of relay 508 to ground at the outer right armature of relay 50 llelay S32 operates. therefore, in response to the operation ol the key for the first digit of the ollice designation. In like manner relays lli 407, L08, 402 and 401i cause the operation of the respective relays 833, S11 and 813 in the sender. These relays all lock to conductor 1104. 

